Digital data communications devices customarily employ one or more serial ports through which digital data messages are interfaced between a resident signalling processor and a serial data communications link to which a remote terminal device is coupled. Because digital data communications may be conducted at a number of different baud rates (e.g. 1200, 2400, 4800, 9600 baud), such devices customarily employ one or both of a software routine and panel DIP (dual in-line packaging) switch through which a user, knowing the baud rate at which communications with a remote terminal device are to be conducted, loads a selected baud rate into an internal register for use by an attendant modem.
Unfortunately, there are variety of applications of digital communications devices, which are to be remotely accessed, in order that an attendant utility device may be conditioned and controlled, without the availability of technical personnel having prior knowledge of the baud rate used by the remote. A non-limitative example of such an application is diagrammatically illustrated in FIG. 1, which shows the distribution of a plurality of remote test equipments or measurement units 11 for monitoring and testing network lines 13 and (subscriber) termination equipment 15 remotely from one or more data terminal units (DTUs) 21, which have the capability of accessing the remote test equipments 11 through attendant modem devices 23, 24 that are linked to a central office 25.
Because the baud rates of the remote data terminal units which may access such equipments are not necessarily known at the time of installation, and indeed can be expected to vary from unit to unit, it is necessary to have a craftsperson perform-on-site (trial and error) adjustment of control switch settings. Moreover, where a remotely accessible piece of equipment contains multiple serial ports, the overall hardware complexity (and therefore cost) of affording baud rate adjustment for each serial port is substantially increased.